The impression is noticeable trough the transparent region from the tiles and encompasses a parallax result when scrolling which supplies an illusion of depth. psychol a notion that's not real to truth, having been altered subjectively in some way while in the head of the perceiver See also hallucination https://elliottwdglo.sasugawiki.com/7163855/everything_about_illusion_of_kundun_mu_online